Encoding keyboard having dual-output shift key

ABSTRACT

An encoding keyboard constructed like that disclosed in U.S. Pat. No. 3,086,635, entitled &#39;&#39;&#39;&#39;Keylever Storage Mechanism,&#39;&#39;&#39;&#39; issued Apr. 23, 1963, to Leon E. Palmer is provided with a novel dual keylever construction that properly time-sequences up and down shift code entries with respect to character entries. The stroke storage provided in the keyboard of U.S. Pat. No. 3,086,635 is expanded to provide storage for two characters, when necessary, to accommodate the characteristically rapid and arhythmic, three-stroke sequence, &#39;&#39;&#39;&#39;upshift-print-downshift.

United States Patent 1 1 3,592,313

[72] Inventors William lLCastle [56] RelerencesCited Winchester; UNITED STATES PATENTS 1N gz'f 'g 3,086,635 4/1963 Palmer 197/16 :5:- 1968 3,273,684 9/1966 0511113361411... 197/16ux [221 My 3,302,764 2/1967 Hickerson 197/16 [45] Patented July 13,1971

. In no am Sm M m 3,348,648 10/1967 Frechette 197/16 [731 Assgme 3,386,554 6/1968 Everhard.... 197/16x 3,422,946 1/1969 Rekewitz 197/16 Armonk,N.Y.

Primary Examiner-Ernest T. Wright, Jr Auomeys l-lanifin & Jancin and E. Ronald Coffman ABSTRACT: An encoding keyboard constructed like that disclosed in U.S. Pat. No. 3,086,635, entitled Keylever Storage [54] ENCODING KEYBOARD HAWNG DUAL'OUTPUT Mechanism," issued Apr. 23, 1963, 16 Leon E. Palmer is prosnm KEY vided with a novel dual keylever construction that properly Claims 2 Drawing Figs time-sequences up and down shift code entries with respect to [S2] U.S. CI 197/71, character entries. The stroke storage provided in the keyboard 197/16, 197/98, [97/107 of U.S. Pat. No. 3,086,635 is expanded to provide storage for [5 I] Int. Cl. B41j /24 two characters, when necessary, to accommodate the charac- [50] Field of Search 197/16, teristically rapid and arhythmic, three-stroke sequence,

7l-80, 98, 99, 106, 107 upshift-print-downshift.

s4 s1 58 f 52 53 o PATENTEUJUL13|97I FIG.1

INVENTORS.

WILLIAM H. CASTLE DONALD L. GREER BY QQWMCLHWM ATTORNEY.

ENCODING KEYBOARD HAVING DUAL-OUTPUT SHIFT KEY DISCLOSURE OF THE INVENTION Typewriters and other keyboard-operated devices usually employ a group of primary keys and one or more precedence,

or case shift keys by which the information content of the primary keys can be increased by a factor of two or more.

In office typewriters, a single shift key is usually provided to define a lower or downshift case when undepressed and to define an upper or upshift case when depressed. It is also common to provide a simple latch to secure the shift key in the depressed position for continued typing in the upper case. In the teletypewriter art it is common to provide a pair of shift keys, one of which defines a lower or letters" case when depressed and the other of which defines an upper or "figures case when depressed.

The usual function of a teletypewriter keyboard is to generate a permutatively significant code representation of key strokes for operating punches, transmitters, and printers. On the other hand, the usual operation of a typewriter is to directly control operation of a mechanically associated 'printer.

In recent years the typewriter and teletypewriter arts have begun to overlap with the result that operators for one type of machine, usually the typewriter, are being employed to operate typewriters having some remote input or output capability heretofore only found in the field of teletypewriters. The IBM 1052 printer-keyboard described in IBM Field Engineering Manual, Form 225-3179-4, published Apr. 1967, by International Business Machines Corporation, Armonk, New York, employs a typewriterlike keyboard that is connected to a printer through electrical connections more typical of teletypewriters than of typewriters. The keyboard includes a typewriterlike shift key that generates an upshift code upon its depression and a downshift code upon its release. Although the keyboard includes a displacement interlock for preventing simultaneous depression of two keys, it possesses no ability to store characters as taught in aforesaid U.S. Pat. No. 3,086,635.

Upon this background it has been an object of our invention to provide a keyboard like that shown in U.S. Pat. No. 3,086,635 with a fully interlocked case shift key capable of generating appropriate code outputs in proper time sequence with other keys of the keyboard.

Another important object of our invention has been to provide a two-character storage mechanism for accommodating the normally rapid and arhythmic sequence upshift-printdownshift," without restricting the individual operators personal style.

A further object of our invention has been to provide a code output keyboard having a shift key device capable of generating either a-discrete shift" code or a shift significant parallel bit to be added to character codes to define the case significance of such character codes.

The objects of our invention are achieved by provision of a main shift keylever and interposer like the keylevers described in aforesaid U.S. Pat. No. 3,086,635, together with a partially similarly constructed auxiliary keylever and interposer. The auxiliary keylever does not include a keybutton, but is driven by a spring in the key depressing direction. Operation of the auxiliary keylever by its depression spring is controlled by a powered interconnection between the interposer ofthe primary shift keylever and the auxiliary keylever. In operation, depression of the primary keylever generates an upshift output via its associated interposer and raises the auxiliary keylever against its spring in preparation for a subsequent cycle. Release of the primary-keylever releases the auxiliary keylever for depression motion by its spring to operate its associated interposer and generate a downshift keyboard output.

As both interposers of the shift key mechanism cooperate with the keyboard displacement interlock, their operation is properly sequenced with the operation of character keys. In the characteristic sequence upshift-print-downshift," the print character key may be struck while the keyboard is still processing the upshift key stroke. The print character thus would be retained in the displacement interlock in a stored condition in accordance with the disclosure of aforesaid U.S. Pat. No. 3,086,635. The shift key, if immediately released, releases the auxiliary keylever which tends to depress its associated downshift interposer by means of its operating spring. The downshift interposer is prevented from operating immediately due to the presence of the character interposer in the displacement interlock. Thus, both the character and the subsequent downshift operations are stored in the keyboard. When the keyboard has completed processing the upshift key entry, it will immediately proceed to process the character entry via the interposer that was in the displacement interlock. As that interposer is removed from the displacement interlock, the auxiliary keylever depression spring will immediately drive the downshift interposer into the displacement interlock. The downshift interposer will in turn be processed immediately following processing of the character interposer. It can be recognized that the sequence of key strokes, including shift key release, for entering this three-character sequence can vary over a wide range of rates and rhythms which could result in a loss of information or interference with the typist in the absence of the two-character storage thus described.

In addition to generating discrete upshift and downshift output codes we have found it useful to provide a further output that identifies the current state of the keyboard at all times. This output is accomplished through use of a reed switch that is selectively operated by the position of the auxiliary keylever. Not only does this position provide a convenient reference for the current shift status of the keyboard, but it also provides an appropriately timed transition of shift state which would not be true if the position of the primary shift keylever itself were observed. For example, where the shift key has been released, but the down shift interposer has not been processed due to a character interposer in the displacement interlock, the primary keylever would indicate a downshift keyboard status, whereas the desired keyboard status is upshift for the character interposer in storage. Only when the character interposer is already being processed and the auxiliary keylever is permitted to be depressed by its spring upon clearance of the displacement interlock, will the case transition of the keyboard be reflected in the keyboard status reed switch.

These and other objects, features and advantages of our keyboard will be better understood by those skilled in the art upon reading of the following detailed description ofa specific embodiment of our inventive concepts wherein reference is made to the accompanying drawing ofwhich:

FIG. 1 is a side elevational view of the basic keyboard construction disclosed in aforesaid U.S. Pat. No. 3,086,635;

FIG. 2 is a fragmentary perspective view of a keyboard constructed in accordance with our invention showing particularly the shift key mechanism thereof.

Referring now more particularly to FIG. 1, there is shown an encoding keyboard 10 having a plurality of finger keys 20 each of which is supported by a keylever 21 that is pivoted to the keyboard frame 10a by a wire 11. Each keylever 21 is manually depressable against a leaf spring 22 from a normal raised position limited by stop bar 12. A pivoted link or dobber 23 is biased by a spring 24 to a position of alignment over an upstanding stud 31 of an output control or encoding interposer 30 shown in its normal, nonselected position. Interposer 30 is mounted by a frame mounted guide rod 13 that is received in an interposer slot 32 for pivotal motion along path P to a selected position 30 and for reciprocating movement along a path P through an output stroke to a position 30" and back to its normal position.

Spring 33 normally retains interposer 30 in its normal position against a leaf spring latch 14. An interposer 30, once moved to its selected position 30', is prevented by spring 14 from returning directly upwardly. A displacement interlock in the form ofa plurality of adjacent aligned balls 15a is positioned in the path of a projection 34 of the interposer to receive the projection 34 as the interposer 30 is moved to its selected position.

The interposer 30 generates a code output as determined by the selective presence or absence of each of several downwardly facing lugs or output projections which respectively engage an associated output code bail 16. As shown in FIG. 2, bails 16 each operate a pivoted shunt 17 made of magnetic conductive material to selectively divert flux from a permanent magnet 18 positioned adjacent to a reed switch 19 to thereby transfer the reed switch 19 and operate a remote data handling circuit (not shown).

To operate the bails 16, the interposers 31) are driven leftwardly in FIG. 1 by a cyclically movable filter shaft or drive member having a pair of diametrically opposite driving surfaces or teeth 41 thereon extending across the keyboard 10 and for engaging an interposer drive surface 36 of any interposer 30 moved to its selected position 30'. Filter shaft 40 is drivingly connected via gears 43 and a one-half revolution cycle clutch 42 with a source of continuously rotating motion as provided by a motor (not shown). The angular spacing between teeth 41 and the rate of rotation of shaft 40 defines the maximum sequential interposer drive rate, or, in other words, the minimum time interval between output codes.

Clutch 42 is controlled by a latch that is pivoted about an axis 51 and is normally urged to a releasing position by a spring 52 acting through a cycle clutch latch link 53. Link 53 is normally prevented from moving by a latch pawl 54 that engages a keeper portion 55 of the keyboard frame 10a. A cycle clutch bail 56 is positioned in the downward path of all interposers 30 of the keyboard 10 and engages the cycle clutch latch pawl 54 whereby downward movement of any interposer 30 will operate the cycle clutch latch pawl 54. When latch pawl 54 is displaced downwardly, pivoting counterclockwise about its axis 57 and against its bias spring 58, and reaches a position of release with respect to the keeper portion 55, the cycle clutch latch link 53 is freed to move leftwardly under force of spring 52, thereby withdrawing cycle clutch latch 50 from a clutch control ledge 4 to cause powered rotation of gearing 43 and filter shaft 411. A cam follower 59 engages a restoring cam 45 on the driven shaft of cycle clutch 42 to restore the cycle clutch latch 51) to its latching position in the path of ledge 44 and permit cycle clutch latch pawl 54 to restore to its holding position with respect to keeper portion 55.

A normal sequence ofa key operation is as follows: Depression of keylever 21 pivots interposer 30 downwardly via dobber 23 to position 30' where projection 34 is received within interlock l5 and the forward end 37 of the interposer 30 is horizontally clear of the latch spring 1 1. Spring 14 thus snaps over the top of the interposer end 37 to retain the interposer 30 in its downwardly pivoted position. Drive surface 36 is now positioned in the horizontal path of tooth 41. Simultaneously with these actions, interposer 30 has displaced cycle clutch bail 56 and latch 54 downwardly to unlatch the cycle clutch latch link 53 for leftward movement via spring 52. Cycle clutch 42 and filter shaft 40 now proceed through 180 of rotation driving the displaced interposer 30 leftwardly and carrying with it all bails 16 for which a downwardly projecting lug 35 is provided. As load is released upon overdriving of tooth 41, interposer 30 will be in leftward position 30" where spring 33 can restore it upwardly and to the right to its original position. If keylever 21 remains depressed, interposer projection 31 strikes the left edge of dobber 23 and pivots the dobber 23 counterclockwise. Thus, depressed keylever 21 must be released before its associated interposer 30 can again be selected. It is particularly important to note that a second keylever, like 21, could have been depressed at any time after the interposer 30 had been driven leftwardly a sufficient amount to remove projection 34 from the displacement interlock 15. The interposer 30, corresponding to the second depressed keylever, would have remained in its selected position stored under leaf spring 141. As cycle clutch 42 approaches the end of its l80 of travel, the stored interposer would have prevented relatching of cycle clutch latch pawl 54 and the cycle clutch 42 would proceed with a second cycle wherein filter shaft 40 would drive the stored interposer 30 leftwardly in a manner similar to operation of the first described interposer 30.

SHIFT KEY MECHANISM The shift key mechanism ofour keyboard is shown in FIG. 2 and employs keylevers and interposers bearing a general resemblance in structure and operation to the keylevers 21. and interposer 30 described in FIG. ll. More specifically, a primary shift keylever 60 pivoted about wire 11, is provided with a manually operable keybutton 61 and with a shift lock button 62 that operates in a conventional manner to retain the shift keylever 60 in its depressed position, when desired. Keylever 60 is biased upwardly against stop bar 12 by a coil spring 63. Keylever 60 operates its associated upshift output control interposer 6 1 via spring biased dobber 65 in a manner identical to the operation described in connection with FIG. 1.

Our shift mechanism is further provided with an auxiliary or supplemental input lever that is also pivoted about wire 11 and cooperates via spring biased dobber 71 with a downshift output control interposer 72 in a manner substantially identi cal to that described in connection with FIG. ll. The auxiliary shift input lever 70, however, is not biased upwardly, but conversely, is biased by resilient spring 73 to its depressed or displaced position. When the typewriter is in its downshift or lower case condition, the parts are positioned as shown in FIG. 2 wherein auxiliary input lever 76 is in its depressed position. Note that dobber 71 is not vertically aligned with the interposer 72, but has been displaced counterclockwise to its noncooperating or nonrepeat position. Input lever 7t) thus can operate interposer 72 only by first being raised against spring 73 to a position allowing dobber 71 to move clockwise over the interposer 72.

The main and auxiliary levers 60 and 70 are interconnected by mechanism including a sliding latch or transfer link 80 mounted parallel with the interposers b4 and 72 and mounted for reciprocating movement on support rod 13 and frame mounting pin 31. Sliding latch 80 includes a horizontal arm 82 that is positioned in the path of upstanding lug 83 ofinterposer 64 so as to be driven thereby upon leftward or output movement of interposer 64 by the filter shaft 41). Sliding latch 80 further includes an upstanding drive part 84 that cooperatively engages an inclined camming bracket 74 attached to the auxiliary keylever 70. When sliding latch 80 is driven to the left by interposer 64, upstanding drive part 841 lifts auxiliary input lever 70 through the camming bracket 74. Note that this lifting action stores energy in spring '73 for a subsequent downward motion of the keylever '70. A latch device 85 is pivoted to the frame 10a and includes a holding tooth 86 that retains the sliding latch 80 in its leftward position when driven thereto by the interposer 64. A bias spring 87 normally urges latch tooth 86 towards its holding position. Latch device 85 further includes an upstanding control arm 88 having a cross pin 89 that overlies the primary keylever 60 to receive oneway motion therefrom. Latch device 85 thus permits complete restoration of interposer 64 while retaining the sliding latch 30 in its leftward position to hold the auxiliary input lever 70 in its upward position.

The parts will remain in the position thus described until keybutton 61 is released. Such release causes keylever 60 to rise, lifting the latch device 85 and releasing the sliding latch 80 from its held position. If auxiliary input lever 70 is free to move, considering the current condition of the displacement interlock 15, spring 73 will drive the lever 70 to its depressed position and camming bracket 74 will restore sliding latch 80 to its rightward position. The displacement of lever 70 thus initiates a keyboard cycle in a manner as described in connection with FIG. ll.

As the interposers 64 and 72 each are provided with characteristic groupings of lugs 35 in accordance with the desired output code, it can be seen that depression and release of keybutton 61 will generate respective codes via the reed switch outputs 19. It is also desirable to indicate the current state of the keyboard 10, as for example, for generating codes discretely identifiable without regard for a precedence code.

For indicating keyboard status, we provide a binary output signal transducer such as a reed switch 90 positioned in the flux path ofa permanent magnet 91. The lower end of auxiliary input lever 70 is formed into a magnetic flux intercepting shunt 92 having two effective positions, one of which is within and the other without the path of flux of magnet 91. Thus, the open or shut reed switch 90 will accurately indicate the status of the keyboard as reflected by the current position of auxiliary input lever 70, and can be sensed by remote circuitry, not shown.

Those skilled in the art will recognize that we have described an improved keyboard of the type disclosed in U.S. Pat, No. 3,086,635, particularly characterized by a unique shift key mechanism. While many features of the shift key mechanism described intercooperate to provide an overall improved operation, it will be recognized that many of these concepts are useful independently of the overall combination.

Having thus described our invention and a preferred embodiment thereof, we claim:

l. A keyboard having a plurality of independent control members each movable along a first path from a normal nonselected position to a selected position, and movable from said selected position only along a second path to an effective output condition and back to its normal nonselected position, a displacement interlock positioned in the first path of said control members for preventing more than one of said control members from reaching its selected position at any one time, power operating means operative in response to the movement of any control member to its selected position to cause movement of any of said control members from their said selected positions at a maximum sequential rate that is independent of the rate of keyboard manipulation, and a manually operable key operatively connected to one of said control members and depressable to cause movement of said one of said control members to its selected position; wherein the improvement comprises:

a supplemental input member operatively connected to a different one of said control members and depressable to cause movement of said different one of said control members to its selection position, and

interconnecting means including said power operating means and responsive to the position of said manually operable key for controlling the depression of said supplemental input member in inverse relation to the depression and release of said manually operable key.

2. A keyboard as defined in claim 1 wherein resilient means biases said supplemental input member toward its depressed position and said interconnecting means comprises;

a transfer link operatively connected to said supplemental input member for moving said supplemental input member against the bias of said resilient means from its depressed position to its nondepressed position, and

means interconnecting said'transfer'link and said one of said control members whereby movement of said one of said control members from its said selected position drives said supplemental input member to its nondepressed position through said transfer link.

3. A keyboard defined in claim I wherein resilient means biases said supplemental input member toward its depressed position and said interconnecting means further comprises:

a latch device operatively connected to said supplemental input member for retaining said supplemental input member in its nondepressed position against the bias of said resilient means, and

means connecting said latch device to said manually operable key for releasing said latch device from its retaining condition with said supplemental input member upon movement of .said key from its depressed to its nondepressed position.

4, A keyboard as defined in claim 2 wherein said interconnecting means further comprises:

a latch device operatively connected to said supplementa input member for retaining said supplemental input member in its nondepressed position against the bias of said resilient means, and

means connecting said latch device to said manually operable key for releasing said latch device from its retaining condition with said supplemental input member upon movement of said key from its depressed to its nondepressed position.

5. A keyboard as defined in claim 1 wherein said timing means comprises:

means establishing a fixed time interval defining said maximum sequential rate.

6. A keyboard as defined in claim 1 further comprising:

a binary output signal transducer responsive to the depressed and nondepressed positions of said supplemental input member for indicating said positions by respective ones of said outputs thereof. 7

7. An encoding keyboard having a plurality of code output bails permutatively operable to define individual items of information, a plurality of manually operable keylevers, a plurality of encoding interposers mounted for reciprocation adjacent said output bails and beneath individual ones of said keylevers, said interposers each having selected different projections thereon for engaging said output bails upon reciprocation to generate an output representative thereof, a drive member extending across said keyboard adjacent one end of said interposers and cyclically movable along a path, latch means normally retaining each of said interposers in a non selected condition out of the path of said drive member, means interconnecting said keylevers and their associated interposers such that depression of a keylever moves its associated interposer along a first path to a position for receiving drive force from said drive member, a displacement interlock positioned in the first path of said interposers for preventing more than one of said interposers from being engaged by said drive member at any one time, means responsive to the displacement of any interposer to its selected position for initiating a cycle of operation of saiddrive member, and a case shift keylever having a normal nondepressed position and movable to a depressed position wherein the improvement comprises:

a first case indicative interposer positioned below said case shift keylever for movement thereby andcooperable with said latch means, said displacement interlock, and said drive member upon depression of said case shift keylever,

a supplemental input lever having a normal depressed position and movable to a nondepressed position,

a second case indicative interposer positioned below said supplemental input lever for movement thereby and cooperable with said latch means, said displacement interlock and said drive member upon movement of said supplemental input lever to its depressed position, and

interconnecting means between said case shift keylever and saidsupplemental input lever responsive to depression of said case shift keylever and including said drive-member for power driving said supplemental input lever from'its depressed to its nondepressed position in response to depression of said case shift keylever, and responsive to release of said case shift keylever for conditioning said supplemental input lever for movement from its nondepressed to its depressed position.

8. A keyboard as defined in claim 7 wherein resilient means biases said supplemental input lever toward its depressed position and said interconnecting means comprises:

a reciprocatable transfer link operatively connected to said supplemental input lever for moving said supplemental input lever from its depressed position to its nondepressed position upon reciprocation thereof, and

means connecting said transfer link to said first case indica- 10. A keyboard as defined in claim 8 wherein said intercontive interposer for transferring reciprocation thereof from necting means further comprises: said drive m mb r o i transfer link to drive Said P- a latch device for retaining said transfer link in its position Plemema] input lever from its depressed to its as driven by said drive member through said first case indepressed Position 5 dicative interposer, and A keyboard as defined in claim 7 wherein resilient means means operatively connecting said latch device with said biases said sPPplememal inPut lever towardlts depressed Posl' case shift keylever for releasing said transfer link from its nonand means conlpnsei retained condition upon release of said case shift keyla latch device operatively connected with said supplemental even input lever for retaining said Supplemental input levir in 11. A keyboard as defined in claim 7 wherein said first case its nondepressed position against the bias of said resilient i means whenever Said case shift keyleveris depressed and indicative interposer and said second case indicative interoperatively connected with Said case Shift keylever for poser each have distinctively coded PI'OjeCUOl'lS cooperable with said output bails for generating distinctive case shift releasing said latch device from its retaining condition d h fb b with said supplemental input lever whenever said case CO es upon reclprocauont ereo ysal five mem shift keylever is released. 

1. A keyboard having a plurality of independent control members each movable along a first path from a normal nonselected position to a selected position, and movable from said selected position only alonG a second path to an effective output condition and back to its normal nonselected position, a displacement interlock positioned in the first path of said control members for preventing more than one of said control members from reaching its selected position at any one time, power operating means operative in response to the movement of any control member to its selected position to cause movement of any of said control members from their said selected positions at a maximum sequential rate that is independent of the rate of keyboard manipulation, and a manually operable key operatively connected to one of said control members and depressable to cause movement of said one of said control members to its selected position; wherein the improvement comprises: a supplemental input member operatively connected to a different one of said control members and depressable to cause movement of said different one of said control members to its selection position, and interconnecting means including said power operating means and responsive to the position of said manually operable key for controlling the depression of said supplemental input member in inverse relation to the depression and release of said manually operable key.
 2. A keyboard as defined in claim 1 wherein resilient means biases said supplemental input member toward its depressed position and said interconnecting means comprises; a transfer link operatively connected to said supplemental input member for moving said supplemental input member against the bias of said resilient means from its depressed position to its nondepressed position, and means interconnecting said transfer link and said one of said control members whereby movement of said one of said control members from its said selected position drives said supplemental input member to its nondepressed position through said transfer link.
 3. A keyboard defined in claim 1 wherein resilient means biases said supplemental input member toward its depressed position and said interconnecting means further comprises: a latch device operatively connected to said supplemental input member for retaining said supplemental input member in its nondepressed position against the bias of said resilient means, and means connecting said latch device to said manually operable key for releasing said latch device from its retaining condition with said supplemental input member upon movement of said key from its depressed to its nondepressed position.
 4. A keyboard as defined in claim 2 wherein said interconnecting means further comprises: a latch device operatively connected to said supplemental input member for retaining said supplemental input member in its nondepressed position against the bias of said resilient means, and means connecting said latch device to said manually operable key for releasing said latch device from its retaining condition with said supplemental input member upon movement of said key from its depressed to its nondepressed position.
 5. A keyboard as defined in claim 1 wherein said timing means comprises: means establishing a fixed time interval defining said maximum sequential rate.
 6. A keyboard as defined in claim 1 further comprising: a binary output signal transducer responsive to the depressed and nondepressed positions of said supplemental input member for indicating said positions by respective ones of said outputs thereof.
 7. An encoding keyboard having a plurality of code output bails permutatively operable to define individual items of information, a plurality of manually operable keylevers, a plurality of encoding interposers mounted for reciprocation adjacent said output bails and beneath individual ones of said keylevers, said interposers each having selected different projections thereon for engaging said output bails upon reciprocation to generate an output representative thereof, a drive member extending across said keyboard adjacent one end of said interposers and cyclically movable along a path, latch means normally retaining each of said interposers in a nonselected condition out of the path of said drive member, means interconnecting said keylevers and their associated interposers such that depression of a keylever moves its associated interposer along a first path to a position for receiving drive force from said drive member, a displacement interlock positioned in the first path of said interposers for preventing more than one of said interposers from being engaged by said drive member at any one time, means responsive to the displacement of any interposer to its selected position for initiating a cycle of operation of said drive member, and a case shift keylever having a normal nondepressed position and movable to a depressed position wherein the improvement comprises: a first case indicative interposer positioned below said case shift keylever for movement thereby and cooperable with said latch means, said displacement interlock, and said drive member upon depression of said case shift keylever, a supplemental input lever having a normal depressed position and movable to a nondepressed position, a second case indicative interposer positioned below said supplemental input lever for movement thereby and cooperable with said latch means, said displacement interlock and said drive member upon movement of said supplemental input lever to its depressed position, and interconnecting means between said case shift keylever and said supplemental input lever responsive to depression of said case shift keylever and including said drive member for power driving said supplemental input lever from its depressed to its nondepressed position in response to depression of said case shift keylever, and responsive to release of said case shift keylever for conditioning said supplemental input lever for movement from its nondepressed to its depressed position.
 8. A keyboard as defined in claim 7 wherein resilient means biases said supplemental input lever toward its depressed position and said interconnecting means comprises: a reciprocatable transfer link operatively connected to said supplemental input lever for moving said supplemental input lever from its depressed position to its nondepressed position upon reciprocation thereof, and means connecting said transfer link to said first case indicative interposer for transferring reciprocation thereof from said drive member to said transfer link to drive said supplemental input lever from its depressed to its nondepressed position.
 9. A keyboard as defined in claim 7 wherein resilient means biases said supplemental input lever toward its depressed position, and said interconnecting means comprises: a latch device operatively connected with said supplemental input lever for retaining said supplemental input lever in its nondepressed position against the bias of said resilient means whenever said case shift keylever is depressed and operatively connected with said case shift keylever for releasing said latch device from its retaining condition with said supplemental input lever whenever said case shift keylever is released.
 10. A keyboard as defined in claim 8 wherein said interconnecting means further comprises: a latch device for retaining said transfer link in its position as driven by said drive member through said first case indicative interposer, and means operatively connecting said latch device with said case shift keylever for releasing said transfer link from its retained condition upon release of said case shift keylever.
 11. A keyboard as defined in claim 7 wherein said first case indicative interposer and said second case indicative interposer each have distinctively coded projections cooperable with said output bails for generating distinctive case shift codes upon reciprocation thereof by said drive member. 